1. Field of the Invention
The present invention generally relates to a heat treating furnace, and more particularly, to a roller hearth type heat treating furnace.
2. Description of the Prior Art
Conventionally, heat treatments of steel materials can be broadly classified into two, in one of which after the materials have been heated up to a predetermined temperature and soaked at this temperature, they are rapidly cooled down (isothermal annealing, normalizing), and in the other of which they are slowly cooled down (full annealing, spheroidize annealing).
In the former, since the temperature difference between a heating zone and a cooling zone is large, a heat insulating intermediate door is generally provided between these zones to substantially partition them from each other.
In the latter, since the temperature difference between adjacent zones is relatively small, these zones are generally partitioned by a partition wall.
As described above, the structure inside the furnace differs, depending upon the heat treatments of the materials. In particular, it is necessary to partition the heating zone and the cooling zone from each other by any suitable partition structure. Accordingly, a most suitable heat treating furnace in a plurality of furnaces is selectively used for heat-treating the materials.
Accordingly, in the present circumstances having a tendency towards the manufacture of many kinds and small quantity, each of the furnaces is low in operating efficiency. Furthermore, the furnaces are frequently brought into operation or to a stop, resulting in increased heat loss and in increased maintenance or inspection work at the time of recommencement of operation.